Killua said Pitou opted fighting an armless Kite over Gon and him, since Kite even without an arm is a considerably better opponent than the two of them, indicating Kite >>> them back at that time. We also know Knuckle is way stronger than that version of Gon and Killua, since even an improved version of them couldn't hope to match up to him, so this is definitely a good fight. I'd give it to Kite though since I think he has an overall better experience in fighting and his special power seems to be more overpower than Knuckle's, imo. High difficulty, though.